Preparation of lubricating greases from unsaturated fatty acid materials



3,000,823 PREPARATION OF LUBRICATIN G GREASES FROM UNSATURATED FATTY ACID MATERIALS Louis A. Clarke, Fishkill, and George W. Eckert, Glenham, N.Y., assignors to Texaco Inc., a corporation of Delaware No Drawing. Filed Mar. 7, 1955, Ser. No. 492,766 11 Claims. (Cl. 252- 35) This invention relates to improvements in the manufacture of lubricating greases from saponifiable materials comprising unsaturated fatty acid materials. More particularly it relates to the manufacture of lithium hydroxy fatty acid greases from unsaturated fatty acid materials.

In accordance with this invention, lubricating greases are prepared from saponifiable materials comprising unsaturated high molecular Weight fatty acids or their esters by a method which comprises subjecting such unsaturated materials to epoxidation and subsequent hydrogenation under controlled conditions. The reaction products thus obtained, comprising chiefly hydroxy fatty acid materials together with smaller amounts of other reaction products, are employed either as the sole saponifiable material or in admixture with other saponifiable materials of the usual type in the grease making. This method is employed with particular advantage in the production of lithium base greases, wherein it affords a means of obtaining lithium base greases of superior properties and permits the use of the convenient low temperature method of saponification and dehydration at temperatures below the melting point of the soap, starting with readily available unsaturated fatty acid materials such as oleic acid and its esters.

The epoxidation reaction is carried out by treating an unsaturated high molecular weight fatty acid or the ester thereof with certain oxidizing agents such as perbenzoic and peracetic acids, which results in the addition of an oxygen atom at the olefinic double bonds, forming the oxirane ring The reaction product contains one or more oxirane rings per molecule, depending upon the degree of unsaturation of the starting material. The reaction is preferably carried out by treating the unsaturated fatty acid material with peracetic acid solution, employing a glacial acetic acid solution as described by Findley et al., J. Am. Chem. Soc. 67, 412 (1945), or in an aqueous acetic acid solution, as described by Terry et al. in US. 2,458,484.

Suitable starting materials for the epoxidation reaction are unsaturated fatty acids containing at least 12 carbon atoms, such as from 12 to about 32 carbon atoms per molecule, and one or more olefinic double bonds, usually from 1 to about 3 olefinic double bonds, per molecule, and the glycerides or other esters of such acids. They may be employed either in relatively pure form or in naturally occurring mixtures with each other and with minor proportions of saturated fatty acids and their esters derived from animal, vegetable or marine oils, such as, for example, lard oil, cottonseed oil, linseed oil, castor oil, menhaden oil, Whale oil, etc. The preferred starting materials are those consisting of at least a predominant proportion of unsaturated fatty acids containing from about 16 to about 24 carbon atoms and either 1 or 2 olefinic double bonds per molecule, such as, for example, oleic acid, elaidic acid, palmitolenic acid, lauroleic acid, palmitolic acids, petroselic acid, linoleic acid, eicosylenic acid, erucic acid and ricinoleic acid, and the esters of such acids.

The hydrogenation is carried out under mild conditions so that at least a major portion of the oxirane groups of the epoxidized material is converted into hydroxyethane groups. The reaction is suitably carried out at temperatures from about 200 F. to about 400 F. in the presence of a nickel catalyst, the preferred conditions varying somewhat with the type of material being treated and the type of grease to be produced. It is generally desirable to avoid high temperatures or unduly prolonged reaction times, in order to prevent other reactions such as esterification between the hydroxy and carboxy groups of the material from taking place to an undesirable extent. In the preparation of lithium base greases, temperatures in the range from about 200 F. to about 300 F. are preferably employed. With temperatures in this range and hydrogen pressures from about 1,000 to about 2,000 pounds per square inch, the reaction is ordinarily complete in about 5 hours, and in a much shorter time when a continuous hydrogenation process is employed. The reaction time is preferably not over about 10 hours. By carrying out the hydrogenation under these conditions, lithium base greases are obtainable which are fully equivalent to lithium l2-hydroxystearate greases, and greatly superior to lithium base greases which have been prepared from other hydroxy fatty acid materials.

The epoxidized and hydrogenated fatty acid material obtained as described above is saponified by any suitable procedure, employing as the saponifying agent a hydroxide, oxide or carbonate of any of the metals ordinarily employed as the metal component of soaps in grease making, particularly the alkali metals and alkaline earth metals such as sodium, lithium, potassium, calcium and barium, as well as certain other metals such as magnesium, zinc, cobalt, manganese, aluminum, lead, etc., and mixtures of two or more such metals. The epoxidized and hydrogenated fatty acid material may be employed either as the sole saponifiable material, or it may be employed in admixture with other saponifiable materials in varying proportions.

In accordance with the preferred embodiment of this invention, lithium base greases are prepared by the low temperature method by saponifying a hydroxy fatty acid material obtained as described above with a basic lithium compound in situ in the presence of a portion of the oleaginous material employed in the grease. The hydroxy fatty acid material may vary advantageously be a hydroxy stearic acid material obtained from oleic acid or its esters by epoxidation and hydrogenation, or a mixture of such material with stearic acid or ester thereof in a proportion of from about 1 to 3 toabout 3 to 1 by weight.

The oleaginous liquids employed in these greases may be any suitable oils of lubricating characteristics, including the conventional mineral lubricating oils, synthetic oils obtained by various refinery processes such as cracking and polymerization, and other synthetic oleaginous compounds such as high molecular weight ethers and esters. The dicarboxylic acid esters, such as di-Z-ethyl hexyl sebacate, di(secondary amyl) sebacate, di-Z-ethyl hexyl azelate, di-isoctyl adipate, etc., are a particularly suitable class of synthetic oils, and may be employed as the sole oleaginous component of the grease or in combination with other synthetic oils or mineral oils. Suitable mineral oils are those having viscosities in the range from about to about 2,000 seconds Saybolt Universal at 100 F., and may be either naphthenic or 'paraflinic in type, or blends of the two.

The greases may also contain various additives of the usual types such as corrosion inhibitors, oxidation inhibitors, antiwear agents, and so forth. Preferably, they contain an oxidation inhibitor which may suitably be an oxidation inhibitor of the amine type, such as diphenylamine, phenylalphanaphthylamine or tetramethyl diamino diphenyl methane.

The following examples are given to further disclose the invention. Examples 2, 3, 4 and 5 describe the preparation of lithium base greases from saponifiable materials comprising chiefly hydroxy stearic acid obtained from oleic acid or glyceride thereof by the method of the invention. Example 1 is illustrative of lithium base greases obtained from saponifiable materials comprising chiefly hydroxy stearic acid obtained from oleic acid by a different method.

EXAMPLE 1 A grease was prepared having the following composition in percent by weight:

Lithium soap 31.5 Mineral lubricating oil 67.9 Phenylalphanaphthylamine 0.6

The saponifiable material was a commercial hydroxystearic acid material which was prepared from oleic acid by the method involving sulfation followed by hydrolysis. This material had a neutralization number of 185, a saponification number of 191, a hydroxyl number of 142 and an iodine number of 8, indicating that it contained approximately 75 percent of hydroxy stearic acid.

The mineral lubricating oil was a refined naphthene base distillate oil having an API gravity of 20.7", a flash point, COC, of 375 F., a Saybolt Universal viscosity of 312 seconds at 100 F. and a pour point of 20 F.

The grease preparation was carried out by the low temperature method, with saponification in situ in the presence of a part of the mineral lubricating oil, employing the theoretical amount of lithium hydroxide, and addition of the remainder of the lubricating oil after dehydration. The method in detail was as follows: A laboratory pestle-stirred grease kettle was charged with 112.5 grams of the hydroxystearic acid material, 112.5 grams of the mineral lubricating oil, 87.5 grams of an aqueous percent lithium hydroxide solution and 150 grams of water. This mixture was heated for one hour with stirring at 200 F., until the saponification was complete, and then at 310 F. for an additional hour to dehydrate. An additional 112.5 grams of the mineral lubricating oil was added to the saponification mass with continued stirring while it was at 310 F., and 22.5 grams more of the oil and 2.25 grams of phenylalphanaphthylamine were added gradually while it was allowed to cool. The grease was drawn at 210 F.

The product obtained was a brown stringy fluid. It contained, by analysis, 0.21 percent free fatty acid (as oleic) and 0.07 percent free alkali (LiOH).

EXAMPLE 2 A grease was prepared having the following composition in percent by weight:

Lithium soap 24.1 Mineral lubricating oil 75.4 Phenylalphanaphthylarnine 0.5

The grease preparation and materials employed were the same as in Example 1 except that the saponifiable material was a hydroxystearic acid material obtained by epoxidation of oleic acid and hydrogenation of the epoxidized product.

The epoxidation reaction was carried out by reacting 4574 grams of a commercial oleic acid with 3120 grams of commercial 40 percent solution of peracetic acid (01. grade) in glacial acetic acid, which had been treated with 3.5 percent of sodium acetate to neutralize the small amount of sulfuric acid present. The oleic acid was added slowly to the solution of peracetic acid with stirring, while the temperature was maintained below 25 C. and the stirring and temperature control continued until the reaction had subsided as evidenced by the l k. o h a ution, requi ng six ou s tota 4 reaction time. The epoxidized product had a melting point of 55 C., a saponification number of 188, and a neutralization number of 186.

Hydrogenation of the epoxidized material was carried out for five hours at a temperature of about 275 F. and hydrogen pressures between 1250 and 2500 pounds per square inch, employing 659 grams of the epoxidized material and 35 grams of Raney nickel in the charge. The hydrogenation product had a saponification number of 186, a neutralization number of 83, a hydroxyl number of 154 and an iodine number of 1.

The saponification was carried out for one hour at 200 F. and the dehydration for one hour at 310 F., as described in Example 1, employing a charge consisting of 225 grams of the hydroxystearic acid material, 225 grams of the mineral oil, 175 grams of 10 percent lithium hydroxide solution and 300 grams of water. After the dehydration, 225 grams more of the lubricating oil were added while the mass was at 310 F. and the grease finished off by stirring in an additional 270 grams of the lubricating oil and 5 grams of phenylalphanaphthylamine during cooling. The product was drawn at 220 F.

A tan uniform buttery grease was obtained having an ASTM worked penetration at 77 F. of 259.

EXAMPLE 3 A grease was prepared of the same composition and in the same manner as described in Example 2 except that a different epoxidized and hydrogenated material was employed, substantially the only difference being that the hydrogenation was carried out for a longer time.

In this case the hydrogenation was carried out for twenty hours at temperatures between 270 F. and 290 F. and hydrogen pressures between 1975 and 2650 pounds per square inch, employing 305 grams of epoxidized material and 16 grams of Raney nickel in the charge. The product obtained had a saponification number of 180, a neutralization number of and a hydroxyl number of 125.

A tan buttery grease Was obtained having an ASTM worked penetration at 77 F. of 332. It contained by analysis, 0.05 percent of free fatty acid (as oleic) and 0.15 percent free alkali (LiOH).

As shown by the above examples, hydroxystearic acid materials obtained from oleic acid by epoxidation and hydrogenation were employed very successfully in grease making, while a satisfactory grease could not be prepared from a hydroxystearic acid material obtained from oleic acid by the hydrolysis method which has been employed heretofore for converting unsaturated fatty acids into hydroxy fatty acids.

The following table gives test results which were obtained upon the greases of Examples 2 and 3.

Table Grease Example 2 Example 3 Dropping point, F 378 370 ASTM Worker Test, penetration at 77 F.

(ASTM) after- 60 strokes 259 332 100,000 strokes 265 315 Norma-Hofimann 0x1 on, 210 F hours,

lbs. drop 1 6 Dynamic water resistance loss, percent- 2 0 Water Immersion Test (MIL-G-3278) Pass Borderline Torque Breakdown Machine Test:

Federal bearing, 250 F.:

Leak g 0 0 65 143 38 43 Overall rating Good Good Tirnken bearing, 250 F.:

Leakage 0 0 Miniature penetration:

riginal; 65 143 Final 63 46 Overall rating Good Good The ASTM Worker Test of the above table was carried out by working the grease in a standard ASTM grease worker for 100,000 strokes. The values obtained are given comparatively with the ordinary ASTM worked penetrations (60 strokes) of the greases.

The Dynamic Water Resistance Test measures the resistance of a grease against being washed out of a ball bearing in the presence of water. It is carried out as described in US. 2,528,373, column 13, lines 25-43.

The Water Immersion Test (MIL-G-3278) is carried out by dipping a sample of the test grease on a stirring rod into boiling water. In order for the grease to pass this test, no cloudiness or evidence of emulsion must be shown after seconds.

The Torque Breakdown Machine Test was carried out employing a standard Federal Precision Ball Bearing No. 1211 and a standard Timken bearing (Cup No. 383 and Cone No. 385), rotated upon a motor driven shaft within a housing provided with temperature control means. The Federal bearing was packed with 32 grams of the test grease, and the Timken bearing with 50 grams of the grease. Each bearing was weighed, and assembled upon the shaft, which was then rotated at 1750 r.p.m. for the Federal bearing and 900 r.p.m. for the Timken bearing for 3 hours, the temperaturebeing raised gradually during the first hour from the initial temperature of 80 F. to 250 F. and then maintained at 250 F. for the remaining two hours. Grease leakage was determined as the difference between the original weight of the grease in the bearing and the combined weight of the grease in the bearing and in the housing at the end of the test.

As shown by the data given in the above table, the grease of Example 2, prepared from the hydroxystearate material obtained by hydrogenation for a relatively short time, had excellent overall properties, including good water resistance and extremely high mechanical stability. The grease of Example 3 also had very good properties generally, but was borderline in its Water resistance as measured by the Water Immersion Test (MIL-G-3278) and hardened slightly upon working, as well as being obtained in poorer yield than the grease of Example 2.

EXAMPLE 4 Lithium soap 16.4 Mineral lubricating oil 81.0 Glycerine 1.8 Phenylalphanaphthylamine 0.8

The epoxidation was carried out substantially asdescribed in Example 2, employing 1200 grams of Star Tallow and 700 grams of a 40 percent solution of peracetic acid. The tallow had a saponification number of 201, a neutralization number of 8.4, a hydroxyl number of 9 and an iodine number of 52. The epoxidized material had a saponification number of 195 and an iodine number of 5.

Hydrogenation of the epoxidized material in a typical run was carried out for 6 hours at temperatures between 200 and 288 F. and hydrogen pressures between 1425 and 2500 pounds per square inch, employing 831 grams of epoxidized material and 47 grams of Raney nickel in the charge. The hydrogenation product had a saponification number of 196, a neutralization number of 20 and a hydroxyl number of 113.

The mineral lubricating oil employed was an oil of the same type as that described in Example 1, having an API gravity of 205, and a Saybolt Universal viscosity of 320 seconds at 100 F.

The grease preparation was carried out in the manner described in Example 2, employing the theoretical amount of lithium hydroxide solution required for complete sapon- EXAMPLE 5 As a further example of this preferred embodiment of the invention, a grease was prepared having the following composition in percent by Weight:

Lithium soap 24.6 Mineral lubricating oil 22.1 Synthetic 01'] 52.6 P-henylalphanaphthylamine 0.7

The saponifiable material employed was a hydroxystearic acid material obtained by the epoxidation of oleic acid and hydrogenation of the epoxidized product as described in Example 2. This material had a saponification number of 188, a neutralization number of 103 and a hydroxyl number of 166.

The mineral lubricating oil was a refined parafiin base distillate oil having an API gravity of 29.0, a flash point, COC, of 367 F., a Saybolt Universal Viscosity of 103 seconds at F. and a pour point of -20 F.

The synthetic ester was di-Z-ethylhexyl sebacate, sold commercially as Plexol 201. This material had a flash point, COO, of 415 F., a kinematic viscosity at 100 F. of 12.4 centistokes, and a pour point below 65 F.

The grease preparation was carried out as described in Example 1, except that the saponification was carried out for two hours at 210 F. The mineral lubricating oil was employed in the original charge, and the synthetic oil was added after dehydration.

A tan buttery grease was obtained, having an ASTM worked penetration at 77 F. at 274.

The above grease had good mechanical stability, water resistance and oxidation resistance. It showed no leakage and little change in penetration after testing in both the Federal and Timken bearings, comparing very favorably in this respect with a lithium 12-hydroxystearate grease of the same grade containing the same lubricating oils and inhibitor. In addition, the grease of this invention softened only slightly to a penetration of 290 after 100,000 strokes in the ASTM Worker Test, while the lithium 12- hydroxystearate grease hardened in this test from a worked (60 strokes) penetration at 77 F of 334 to 293 after 100,000 strokes.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof and, therefore, only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. The method of preparing lubricating greases from unsaturated fatty acid materials as the saponifiable materials which comprises epoxidizing an unsaturated fatty acid material of the class consisting of high molecular weight fatty acids containing an olefinic double bond and the esters thereof so as to convert at least a major portion of the olefinic double bonds into oxirane groups, hydrogenating the resulting epoxidized material under mild conditions so as to convert at least a major portion of the oxirane groups into hydroxyethane groups, saponifying with a metal compound the resulting hydrogenated product and thickening an oleaginous liquid lubricating base to a grease consistency with the resulting saponification product.

2. The method according to claim 1 wherein the said unsaturated fatty acid material is selected from the class consisting of fatty acids containing from 16 to 24 carbon atoms and 1 to 2 olefinic double bonds per molecule and the esters of such acids.

3. The method according to claim 1 wherein the said metal compound is selected from the class consisting of basic alkali metal and alkaline earth metal compounds.

' 4. The method according to claim 1 wherein the hydrogenation is carried out with a nickel catalyst at temperatures between about 200 F. and 400 F.

5. The method of preparing lubricating greases from unsaturated fatty acid materials as the saponifiable materials which comprises epoxidizing an unsaturated fatty acid material of the class consisting of fatty acids containing from 1-6 to 24 carbon atoms and 1 to 2 olefinic double bonds per molecule and the esters thereof so as to convert at least a major portion of the olefinic double bonds into oxirane groups, hydrogenating the resulting epoxidized material with a nickel catalyst at temperatures between about 200 F. and 300 F. until at least a major portion of the oxirane rings are converted into hydroxyethane groups, saponifying with a metal compound the resulting hydrogenated product and thickening an oleaginous liquid lubricating base to a grease consistency with the resulting saponification product.

6. The method according to claim 5 wherein the said unsaturated fatty acid material is selected from the class consisting of oleic acid and its esters.

7. The method according to claim 5 wherein the said hydroxy fatty acid material is saponified in admixture with a fatty acid material selected from the class consisting of high molecular Weight fatty acids and esters thereof in a ratio of hydroxy fatty acid material to fatty acid material from about 1 to 3 to about 3 to 1.

8. The method according to claim 5 wherein the hydrogenation is carried out for a period not in excess of about 10 hours.

9. The method according to claim 5 wherein the satponification is carried out in situ in a portion of the lubrieating oil employed in the grease and the grease preparation is carried out at temperatures below the melting point of the soap.

10. A lubricating grease thickened to a grease consistency with a lithium soap of a hydroxy fatty acid material obtained by epoxidizing an unsaturated fatty acid material of the class consisting of fatty acids containing from 16 to 24 carbon atoms and l to 2 olefinic double bonds per molecule and the esters thereof so as to convert at least a major portion of the olefinic double bonds into oxirane groups, and hydrogenating the epoxidized material with a nickel catalyst at temperatures between about 200 F. and 300 F. until at least a major portion of the oxirane groups are converted into hydroxyethane groups.

11. A lubricating grease according to claim 10 wherein the said unsaturated fatty acid material is oleic acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,443,280 Swern et al June 15, 1948 2,492,201 Swern et al Dec. 27, 1949 2,607,734 Sproule et al Aug. 19, 1952 2,607,735 Sproule et a1 Aug. 19, 1952 2,651,616 Mathews et al Sept. 8, 1953 2,712,527 Mikeska et al July 5, 1955 2,719,124 Mikeska et al Sept. 27, 1955 OTHER REFERENCES Findley et al., I. Am. Chem. Soc. 67, 412 (1945). 

1. THE METHOD OF PREPARING LUBRICATING GREASES FROM UNSATURATED FATTY ACID MATERIALS AS THE SAPONIFIABLE MATERIALS WHICH COMPRISES EPOXIDIZING AN UNSATURATED FATTY ACID MATERIAL OF THE CLASS CONSISTING OF HIGH MOLECULAR WEIGHT FATTY ACIDS CONTAINING AN OLEFINIC DOUBLE BOND AND THE ESTERS THEREOF SO AS TO CONVERT AT LEAST A MAJOR PORTION OF THE OLEFINIC DOUBLE BONDS INTO OXIRANE GROUPS, HYDROGENATING THE RESULTING EPOXIDIZED MATERIAL UNDER MILD GENATING THE RESULTING EPOXIDIZED MATERIAL UNDER MILD OXIRANE GROUPS INTO HYDROXYETHANE GROUPS, SAPONIFYING WITH A METAL COMPOUND THE RESULTING HYDROGENATED PRODUCT AND THICKENING AN OLEAGINOUS LIQUID LUBRICATING BASE TO A GREASE CONSISTENCY WITH THE RESULTING SAPONIFICATION PRODUCT. 